Bag making machine

ABSTRACT

This patent discloses apparatus for forming bags from a web of heat sealable stock, such as thermoplastic, the apparatus including feed rolls for feeding, at a constant predetermined rate, the web of stock over a sealing cylinder. The sealing cylinder includes a combination reciprocating knife and sealing member for severing the web transversely of its length while sealing areas of the plys along both of the severed edges. By driving the sealing cylinder with eliptical gears and at the proper timed relation, the velocity of the web across the cylinder is reduced, relative to the web feed, during engagement of the web with the sealing and severing knife, the rotation of the cylinder being faster during the remaining portion of one revolution in which the sealing cylinder is not effecting a seal or severance of the web.

United States Patent [1 1 Emond 1 Feb. 26, 1974 BAG MAKING MACHINE [22] Filed: May 18, 1972 [21] Appl. No.: 254,758

[58] Field of Search..... 93/33 H, DIG. l, 8 R, 33 R, 93/35 R, 19, 26; 156/515, 498; 219/1053, 10.77; 83/313, 324

[56] References Cited UNITED STATES PATENTS 1,489,135 4/1924 Langston 83/324 X 3,522,689 8/1970 Wylie et al 93/33 H UX 1,997,608 4/1935 Swift, .lr..... 83/324 X 3,347,119 10/1967 Sarka 83/313 X 2,978,008 4/1961 Conti 93/DIG. 1

3,059,690 10/1962 Nyborg 93/DlG. 1 2,737,859 3/1956 Allison et al 93/8 R 2,670,783 3/1954 Moravec et a1 93/DIG. 1

Primary ExaminerRoy Lake Assistant Examiner-James F. Coan Attorney, Agent, or Firm-William J. Dick 5 7 ABSTRACT This patent discloses apparatus for forming bags from a web of heat sealable stock, such as thermoplastic, the apparatus including feed rolls for feeding, at a constant predetermined rate, the web of stock over a sealing cylinder. The sealing cylinder includes a combination reciprocating knife and sealing member for severing the web transversely of its length while sealing areas of the plys along both of the severed edges. By driving the sealing cylinder with eliptical gears and at the proper timed relation, the velocity of the web across the cylinder is reduced, relative to the web feed, during engagement of the web with the sealing and severing knife, the rotation of the cylinder being faster during the remaining portion of one revolution in which the sealing cylinder is not effecting a seal or severance of the web.

35 Claims, 10 Drawing Figures PAIENTEDFEBZSIHH SHEET 1 (If 4 FIGJ SHEET 3 (1F 4 BAG MAKING MACHINE SUMMARY OF THE INVENTION AND STATE OF THE PRIOR ART The present invention relates to bag making machines, and more particularly to a bag making machine which permits of continuous feeding of a tubular web of heat sealable material while effecting severing and sealing along both of the severed edges without stopping the motion of the machine.

In conventional bag making machines, such as disclosed in the Binnall US. Pat. No. 2,707,985, bags are formed from a continuous strip of tubular thermoplastic film stock which is advanced a distance equal to the length of two bags on each feed of the strip material. During each dwell between successive feeds of the stock, a weld bar is operated to seal the ends of two bars simultaneously and at the same time to sever the stock between the welds by the action of heat and pressure applied to the material by the weld bar. In other bag forming machines, a continuous length of tubular, thermoplastic film stock is advanced the length of a single bag, then a dwell occurs during which time the material is sealed transversely of its length by a heated bar. A knife is operated simultaneously with the weld bar to cut off the material adjacent the seal.

In either type of machine it is essential that the sealing and/or severing action occur during a dwell period which, of course, limits the throughput of the machine. Furthermore, much of the present day machinery requires that the machine be down for extensive lengths of time in order to change the length of the bag which is being formed thereon. Additionally, it is conventional practice to seal the bags by applying heat from above which means that the sealing and severing bar must be at a high temperature which increases wear, decreases life and increases power requirements for the apparatus.

In the bag making machine of the present invention, the feed rate of the web is continuous while the velocity of the web through the means for severing the web transversely of its length and for sealing areas of the plys along both of the severed edges thereof, is slowed during sealing and severing and then moved more rapidly during the nonsealing portion of the rotation of the sealing cylinder.

In view of the above, it is a principal object of the present invention to provide an economical bag making machine which is capable of producing bags from a web. of heat sealable materialmore quickly than present state of the art bag making machines.

Another object of the present invention is to provide a bag making machine in-which a heat sealable plastic web may be advanced continuously through the machine without stopping the machine during the sealing and severing actions.

Still another object of the present invention is to provide a bag making machine having a rotatable sealing cylinder and-drive means to effect rotation of the cylinder at differing rates of rotational speed during one revolution thereof.

Yet another object of the present invention is to provide a novel bag making machine in which the length of the bags being'fabricatedon the machine may be varied with a minimal of down time so as to minimize lossof production.

Another object of the present invention is to provide a severing and sealing means in the sealing cylinder underlying the heat sealable material rather than being superimposed thereof.

Yet another object of the present invention is to provide a novel heat sealing and severing means for effecting a severance and weld of heat sealable material to thereby form bags, in which the heat sealing means is operated in timed relation with the rotation of the sealing cylinder and engages the stock during at least a portion of a revolution of the cylinder.

Yet another object of the present invention is to provide a novel bag making machine in which the bags are easily removed and fed to a point distant or removed from the sealing cylinder so as to facilitate further handling.

Yet another object of the present invention is to provide a novel bag making machine which is easily fabricated and manufactured from standard parts.

Other objects and a fuller understanding of the invention may be had by referring to the following specification and claims taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagrammatic view of apparatus constructed in accordance with the present invention;

FIG. 1A is a fragmentary perspective view of typical heat sealable stock and bag formed on the apparatus of the present invention;

FIG. 2 is an enlarged fragmentary plan view illustrating generally the placement of parts of a portion of the apparatus illustrated diagrammatically in FIG. 1 and constructed in accordance with the present invention;

FIG. 3 is an enlarged fragmentary sectional view taken along line 3--3 of FIG. 2;

FIG. 4 is a fragmentary sectional view similar to that illustrated in FIG. 3 but showing the apparatus in a different position;

FIG. 5 is an enlarged fragmentary sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is a fragmentary schematic side elevational view showing the manner in which the apparatus is driven;

FIG. 7 is a fragmentary side elevational view of a portion of the apparatus illustrated in FIG. 6 and showing means for varying the bag length;

FIG. 8 is a fragmentary sectional view of the apparatus illustrated in FIG. 7; and

FIG. 9 is a fragmentary sectional view taken along line 9-9 of FIG. 5, and as if FIG. 5 were not in section.

Referring now to the drawings and more specifically FIG. 1 thereof, a schematic diagrammatic representa-. tion of apparatus 10, constructed in accordance with 1 the present invention, is illustrated therein. As shown, the apparatus includes web supply means, in the illustrated instance a supply roll 11 of heat sealable material 12 such as thermoplastic sheet stock which is folded longitudinally so as to form a fold line 12A along one longitudinal edge of the stock (FIG. 1A). The fold line forms the bottom of the bag B and makes the web substantially tubular in cross section. The web or stock 12 is pulled from the supply roll 11 as by feed means 13, in the'illustrated instance a pair of web feed rolls 13A, 13B positioned on opposite sides of the web. The web then passes between slip rolls 14 including upper and lower rolls 14A, 14B and then into sealing means 20, in the illustrated instance comprising a rotatably mounted sealing cylinder drum or roll 21. The sealing cylinder cooperates with a synchronously driven seal bar carrier 50 to effect at least a partial severance and a heat seal of the overlying superimposed plys of the web adjacent to and along the opposite sides of the partially severed web. The bags thus formed (commonly referred to as side weld bags) are removed from the cylinder onto a bag discharge means 75, in the illustrated instance including a pair of conveyors 76, 77 which serve to transport the bags for placement at a position remote from the sealing cylinder 21.

In accordance with the invention the feed means 13 supplies the web 12 to the sealing means 20 at a constant speed, the sealing cylinder rotating at a variable rate during one revolution and in timed synchronism with the seal bar carrier 50 so as to effect at least a partial severance, in the present instance a severing of the stock laterally of the web 12 while sealing opposite lateral edges of adjacent plys of the web 12 as it passes across the sealing cylinder 21. To this end and referring first to FIG. 2, the apparatus is mounted on spaced apart upstanding frame members and 16 which serve as ground support for the apparatus. As illustrated, the feed means or rolls 13 are journaled in the frame members 15 and 16 and are driven for feeding the web 12 in the direction of the arrow 17. The slip rolls 14 are also shown adjacent the feed rolls 13 and are also driven, in the present instance overspeed, to provide a uniform tension on the web 12, closer to the cylinder 21, as it is being fed by the feed rolls 13.

Intermediate the upstanding frame members 15 and 16 and mounted for rotation with respect thereto is the sealing cylinder 21 which includes axially extending outboard shaft portions 22 and 23 extending from the axial terminal ends 22A, 23A of the sealing cylinder and which are journaled for rotation in the upstanding frame members 15 and 16. As illustrated, the cylinder includes, in the present instance, a plurality of circumferentially extending axially spaced apart grooves 24 having intermediate land portions 25 therebetween. The shaft 22, which extends outboard of the frame 15, is connected to differential drive means 30, in the present instance comprising elliptical gears positioning of which and operation of which will be described more fully hereinafter. Suffice to say at this time that the purpose of the differential drive means is to effect a different rotational velocity to the drum, roll or sealing cylinder 21 during one revolution thereof so that at certain times during one revolution, the sealing cylinder will be moving faster than the feed of the web 12 and at certain other times will be moving more slowly but without variations in the feed rate dictated by the feed means or feed rolls 13.

As heretofore described, sealing and severing means are provided in the sealing cylinder 21 which cooperate with a synchronously driven seal bar carrier 50 to effect at least a partial severance, in the illustrated instance a complete severance, and a heat seal of the overlying superimposed plys of the web adjacent to and along the opposite sides of the severed web. To this end, and referring first to FIG. 2, mounted on the shafts 22 and 23 extending from the terminal ends 22A and 23A respectively of the sealing cylinder 21 are driven sprockets 25 and 26 respectively, the sprockets being connected to the shafts 22 and 23 for rotation therewith by the differential drive means 30. The drive sprocket 25 engages a chain 51A (see FIG. 3) looped around sprockets 25A, 25B and a third sprocket 25C. In a like manner, a similar chain is looped around drive sprocket 26 and sprockets 26A, 26B and a third sprocket (not shown) which is on a common shaft 29 with sprocket 25C. As illustrated in FIG. 2, the sprocket 25A is connected to a common shaft 27 with sprocket 26A, while sprocket 25B is connected with sprocket 26B to a common shaft 28, the shafts 27 and 28 being journaled in the frames 15 and 16 for rotation. Intermediate the chains driven by the drive sprockets 25 and 26, and carried by the chains is a seal bar 52 which cooperates with the sealing and severing means associated with the sealing cylinder 21 to sever the web 12 and heat seal the overlying superimposed plys of the web adjacent to and along the opposite sides of the web. Inasmuch as the sprockets are connected to the sealing cylinder 21 and rotate therewith, the seal bar 52 is driven in timed synchronism with the rotation of the sealing cylinder 21.

In order to sever and seal to form individual side weld bags, the sealing and severing means is carried by the sealing cylinder and is adapted to engage the web 12, cooperating with the seal bar 52, during each revolution of the sealing cylinder 21. To this end and referring to FIGS. 2, 3 and 5, a channel 53 extends axially of the cylinder 21 communicating with the peripheral surface thereof. The channel houses sealing and severing means, in the present instance comprising a heated severing knife 54 mounted for reciprocation in the channel 53. A shaft 55, extending axially through the cylinder, is connected to a crank 56 at one outboard end, and another crank 57 at the other outboard end, the cranks having their extended ends connected to the axially extending reciprocatable knife 54. As shown best in FIGS. 2 and 4, the shaft 55 extends through the sprocket 25 and is connected to a bell crank 58 having a cam follower 59 thereon which rides on the surface 60A of a cam 60. As shown, the cam is connected to the inside upstanding surface 15A of the frame 15. As illustrated best in FIG. 3, the cam 60 has an elevated portion 61 which is engaged by the cam follower 59 thereby causing clockwise rotation of the bell crank 58 (FIG. 3) and thus the crank 56 upon engagement of the follower with the elevated portion 61. The camming action effects an elevation of the knife 54 against the underside of the web 12. Inasmuch as the seal bar 52 is moving in timed relation with the sealing cylinder 21, the heated knife 54 presses against the web and the seal bar 52, effecting a severance as well as side seals of adjacent portions on opposite sides of the severed edge causing a seal of the superimposed overlying plys.

When the knife employed is to effect a complete severance of the web 12 as well as adjacent side seals, such as by the knife 54, the seal bar is preferably composed of a low durometer rubber wrapped in heat resistant material such as a teflon impregnated glass cloth. The rubber gives resilience to the structure while the cloth acts as a heat barrier to the knife 54.

As will be described later with reference to FIG. 6, during the portion of one complete revolution of the sealing cylinder 21 in which the knife 54 engages the underside of the web and presses therethrough against the sealing bar 52, the sealing cylinder is moving at its slowest speed so as to permit a sufficient time of engagement with the web 12 to effect a successful sealing of the adjacent superimposed plys of the webs forming the side seal of the bag. When the cam follower 59 comes off the cam high point 61, biasing means, in the illustrated instance a spring 62, causes the bell crank to rotate counterclockwise depressing the knife 54 slightly below the outer circumferential surface of the sealing cylinder 21 (see FIG. 4).

In order to insure separation of the bags from the surface of the cylinder 21, stripping means are provided for disengaging the bag from the surface of the cylinder. To this end and as best viewed in FIGS. 2-4, a plurality of stripping wheels 78 and interdigitated belts 79 associated with conveyor 77, are mounted on a rotatable shaft 80 which extends axially of the cylinder 21 adjacent the periphery thereof. As shown, the wheels 78 ride in the grooves 24 in the surface of the cylinder 21. In this manner, when a bag, which tends to stick to the surface of the cylinder, comes into contact with the wheels 78, the bag is peeled off the cylinder by the wheels causing the bag to be stripped from the surface of the cylinder.

Inasmuch as the stripping wheels 78 are located within the grooves 24, means are provided to move the wheels out of the grooves to effect clearance of the wheels when the knife blade passes adjacent the wheels. To this end, and as best illustrated in FIGS. 2 and 4, on either end of the cylinder 21, overlying the groove 53 for the sealing severing means, is a cam 81 which is adapted to engage a cam follower 82 circumferentially aligned with the cam 81 and on the shaft 80. The shaft 80 is connected to one arm 83A of a bell crank 83 which is rotatably mounted on a pivot 84 connected to the frames and 16 respectively. The other arm 83B of the bell crank is connected to biasing means, in the illustrated instance a tension spring 85 which serves to pivot the bell crank 83 to maintain engagement of the wheels 78 in the grooves 24 of the cylinder 21. As the cam 81 engages the cam follower 82, the wheels 78 rotate to the dashed line position (FIG. 4) clearing the surface of the cylinder 21 and preventing engagement of the heated knife 54 against the surface of the wheels. As viewed in FIG. 4, the camming action effects a clockwise movement of the bell crank 83 about the pivot point 84, the spring 85 causing the wheels 78 to be restored to a nonnal position.

The drive for the apparatus may be taken from single drive motor to effect a constant speed rotation of the web feed rolls while a variable speed power take off may be employed to permit of a variation in the speed applied to the differential drive means 30, heretofore alluded to, to facilitate changes in bag length. To this end and referring now to FIG. 6, drive means, in the present instance comprising a variable speed drive motor 40, is coupled to a main drive shaft 42 by a drive belt 41. The main drive shaft is mounted for rotation intermediate the upstanding frame members 15 and 16. A pulley 43 and belt 43A act as a power takeoff to drive a pulley 44 connected through the frame 15 to roll 13B of the web feed rolls 13. An additional pulley 45, through drive belt 45A, connects the roll 14B of the slip rolls 14 for driving rotation at a faster rotational speed than the speed of the drive rolls 13. However, the slip rolls are appropriately named as they serve to feed the web 12 at a point closely adjacent the periphery of the sealing cylinder and have the ability to slip when feeding the web because of less frictional engagement than the frictional engagement between the rolls 13A and 13B of the feedrolls 13.

In order to permit variations in the speed of the sealing cylinder 21 relative to the web feed, the main drive shaft 42 is provided with a gear 46 which drives a variable speed drive 47. The variable speed drive may be of any type sufficient to handle the load of the sealing cylinder gear train, hereinafter described. A suitable variable speed drive is the PIV drive made by Link Belt Company of Philadelphia, Pennsylvania. The variable speed drive 47 is connected to the differential drive means 30 by a gear 48 which is mounted on a shaft 48A connected to the frame 15. The gear 48 drives a second gear 49 which is mounted for rotation on a shaft 49A connected to the frame 15, and which acts as the driver gear for the differential drive means 30.

The differential drive means 30 is adapted to effect a varying rotational velocity to the sealing cylinder 21 during each revolution thereof. To this end, and as shown in FIG. 6, the differential drive means comprises a pair of elliptical gears, the first gear 31 being mounted for rotation on the shaft 49A and coupled to the second gear 49, while a second elliptical gear 32 is adjustably coupled to the shaft 22 extending from the sealing cylinder 21. As shown in FIGS. 6 and 7, the elliptical gear may be substantially circular and include an offset axis of rotation, the axis in the illustrated instance, for illustration purposes only, being approximately one-fourth the diameter of the gear. (It should be recognized that in order to mesh properly, the gears must have identical axis). The gears effectively operate so that the effective radius (and thus the diameter) of both the driving elliptical gear 31 and the driven elliptical gear 32 is constantly changing with regard to its axis of rotation. This means that in the condition, such as illustrated in the position of the gears shown in FIG. 6, elliptical gear 31 has an effective radius R1 equal to the distance from axis 49A to the point of mesh between the two gears, and thus a diameter equal to that of a gear having a diameter of 2R1. On the other hand, the effective size of the gear 32, in the position illustrated in FIG. 6, is a gear with a diameter equal to 2R2. In effect, therefore, when the gears are in the position shown in FIG. 6, a large gear 31 is driving a very small gear 32, and the sealing cylinder, connected through shaft 22 to the elliptical gear 32, is rotating at maximum velocity. Alternatively, when the gears have rotated from the position illustrated in FIG. 6, R1 will be small while R2 will be large and the effective ratio of the gears will have changed such that the velocity of the sealing cylinder is now at a minimum.

As may be seen from the foregoing, if the seal bar 51 of the seal bar carrier 50 is timed along with the sealing and severing means so that sealing and severing occurs when R1 is substantially minimum and R2 substantially maximum, or at that very small arc of the cylinders rotation just before and after that condition exists, then the sealing cylinder rotational velocity will be at its slowest when sealing and severing occurs. Alternatively, when the seal bar 51 is disengaged from the sealing and severing means, the rotation of the sealing cylinder is at its faster portion of one rotation. As long as the surface speed of the sealing cylinder is faster during at least one portion of one revolution than the feed of the web, as dictated by the feed rolls 13, even though the velocity when sealing and severing may be slower, bags may be formed without changing the velocity of the feed.

1 In order to properly time the sealing cylinder 21 to the differential drive means for proper bag length, the position of the elliptical gears must be adjusted to the appropriate position of the sealing bar and severing and sealing means associated with the sealing cylinder. To this end, one of the differential drive means and sealing cylinder is made adjustable with respect to the other to facilitate proper timing when effecting changes in bag length. Referring now to FIGS. 7 and 8, the elliptical gear 32 includes adjustable coupling means 33 which rigidly but adjustably couples the shaft 22, extending from the sealing cylinder 21, to the gear 32. As best illustrated in FIG. 8, the shaft 22 includes a reduced diametrical portion 22A having a threaded end 22B which extends through a bore 34 in .the gear 32. The bore 34 includes a tapered portion 34A which receives wedge means, in the present instance a frustoconical member 35 having a central bore portion 36 of sufficient diameter to fit over the shaft portion 22A and register with the tapered portion 34A of the bore 34. The wedge 35 includes a key or the like 36A which registers with a slot 22C in the portion 22A of the shaft 22, coupling the frustoconical wedge member to the shaft. A threaded nut 37 registers with the threaded portion 22B of the shaft portion 22A and serves to force the frustoconical wedge member 35 into the tapered portion 34A and lock the gear 32 to the shaft 22.

As illustrated best in FIG. 7, the wedge 35 has a dial face 38 with indicia thereon indicating bag length, the indicia registering with a pin 39 in the gear 32 indicating the position of the gear 32 relative to the sealing cylinder 21. When adjustment is necessary, it is a simple matter to loosen the nut 37, releasing compression of the frustoconical member in the tapered bore 34A, and then rotate the sealing cylinder 21 to change the position of the indicia on the dial plate 38 relative to the pin marker 39. In this manner, rapid setup as well as changes in bag length may be easily facilitated.

By utilizing the knife 54 below the web, the temperature of the knife may be lower than in state of the art type machines. However, the heat generated by the knife may create heat problems in the surface of the sealing cylinder which may cause sticking of the web 7 material to the surface of the cylinder. To prevent sticking of the thermoplastic material against the cylinder, it is desirable to provide cooling means for the cylinder. To this end and referring now to FIGS. 5 and 9, one-half 90A of a rotary cooling gland 90 is connected as by bolts or the like 91 to the frame 16, the other, rotatable half 90B, being keyed as at 92 to the shaft 23 at one end of the sealing cylinder 21. An inlet 93 to which a cooling fluid such as water may be applied, connects to the first half or fixed portion 90A of the gland 90 and leads as by a conduit or the like 94 into a first annular cavity 95 which is coextensive with both halves 90A and 90B of the gland 90. Tubing 96 is coupled to the cavity 95 and extends through the bore 23B of the shaft 23 into a distribution manifold 97 which divides the fluid flow through a plurality of coils, in the present instance three coils designated 98A, 98B and 98C, disposed adjacent the interior of the surface of the cylinder. The flow meets at a collection manifold 99 and then through tubing 100 into a second annular cavity 101, also coextensive with the two halves 90A and 90B of the gland 90. The liquid is then discharged as through an outlet 103.

As may be seen in FIG. 5, the second portion 908 of the gland is biased against the first or fixed portion of the fixed portion 90A as by a stop member 104, rigidly secured to the shaft 23 as by a set screw 105, and a biasing spring 106 which engages the second half 90B of the gland 90 effecting a face-to-face seal of the gland halves. Sealing of the gland halves is accomplished by 0 rings 107 which are positioned intermediate the two halves and inhibit leakage. It should be recognized that the cooling system illustrated is only by way of example, there being numerous commercially available cooling systems as well as numerous glands and water bearings (or the like) which permit rotational movement while cooling the rotatable member.

In order to provide proper heating of the knife 54, an element 54A extends axially of the knife and is substantially coextensive therewith. The element 54A is powered in a conventional manner as by slip rings 110, 111 from conventional brush members 110A and 111A mounted in a block 112 connected to the frame 16. In a like manner, additional slip rings 113 and 144 may be provided for connection to thermocouples and the like (not shown) to monitor the temperature of the cylinder and/or the knife, as desired. It should be recognized that inasmuch as the rings 111-114 are rotating, simple wire connections to the rotating cylinder or knife are easily made inasmuch as those wires are rotating also.

Thus the apparatus of the present invention may be utilized to make bags continuously without changing the feed rate of a web of thermoplastic material. This is accomplished by providing differential drive means for the sealing cylinder, the differential drive means providing a differential rotational speed of the sealing cylinder during each revolution so as to permit severance and sealing of the web without slowing the feed rate or stopping the cylinder.

Although the invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction, the combination and arrangement of parts and the mode of operation may be made without departing from the spirit and the scope of the invention as hereinafter claimed. I

What is claimed is:

1. Apparatus for sealing and severing adjacent superimposed plys of a web of heat sealable material, said apparatus comprising: web feeding means for supplying said web at a predetermined rate to a severing means; and sealing means associated with said severing means for sealing plys along both of the severed edges thereof; means for reducing the velocity of said web as it passes through said severing means without stopping the movement of said web.

2. Apparatus in accordance with claim 1 including a sealing cylinder, drive means to effect rotation of said cylinder, and means to effect differing rates of rotational speed to said cylinder during one revolution thereof.

3. Apparatus in accordance with claim 2 wherein said severing and sealing means are in said cylinder, a heat sealing bar connected in timed relation with the rotation of said cylinder and means to effect engagement of the severing and sealing means in said cylinder and said sealing bar through said plys of heat sealable material during at least a portion of one revolution of said cylinder.

4. Apparatus in accordance with claim 2 wherein said severing and sealing means is positioned in said cylinder along one side of said web, and means for reciprocating said severing means for engagement and disengagement with said web.

5. Apparatus in accordance with claim 4 including a heat sealing bar connected in timed relation with the rotation of said cylinder and along the opposite side of said web; and means to effect engagement of the severing and sealing means with said sealing bar through said plys of heat sealable material during at least a portion of each revolution of said cylinder.

6. Apparatus in accordance with claim 5 wherein said sealing means underlies said web.

7. Apparatus in accordance with claim 4 wherein said web is engaged by said severing means during the slower portion of the rotational speed of said cylinder.

8. Apparatus in accordance with claim 2 wherein said drive means includes a drive motor, and said means to effect differing rates of rotational speed comprises a pair of meshing elliptical gears.

9. Apparatus in accordance with claim 8 including variable speed drive means intermediate said drive motor and said elliptical gears.

10. Apparatus in accordance with claim 2 wherein said means for sealing said plys is integral with said severing means.

11. Apparatus in accordance with claim 10 wherein said severing means comprises a knife extending laterally of said cylinder, and means to heat said knife.

12. Apparatus in accordance with claim 11 including cooling means in said cylinder.

13. Apparatus in accordance with claim 2 including a discharge conveyor for discharging severed and sealed bags from said cylinder.

14. Apparatus in accordance with claim 2 including stripping means cooperating with said cylinder to strip bags from said cylinder.

15. Apparatus in accordance with claim 14 including means defining lands and grooves in the surface of said cylinder, said stripping means comprising a plurality of wheels mounted for rotation in said grooves, and for removing bags from the lands.

16. Apparatus in accordance with claim 15 wherein said wheels are mounted on a shaft, and bag discharge conveying means rotating said shaft in the same direction as said cylinder.

17. Apparatus in accordance with claim 15 wherein said severing and sealing means comprises a heated knife, means in said cylinder for receiving said knife, and means to reciprocate said knife between a recessed position below the surface of said cylinder and an elevated position for engagement and disengagement with said web.

18. Apparatus in accordance with claim 17 including cam means for disengaging said wheels from said grooves at least when said knife underlies said wheels.

19. Apparatus in accordance with claim 2 wherein said means to effect differing rates of rotational speed comprises a pair of meshing gears having offset axes of rotation, and means to effect an adjustment of the rotational position of said gears relative to said cylinder.

20. Apparatus in accordance with claim 19 wherein said cylinder includes a shaft mounted for rotation in a frame, and said means to effect adjustment of the rotational position of said gears comprises a wedge connected to one of said shaft and one of said gears, and means to releasably couple said wedge to said shaft.

21. Apparatus in accordance with claim 20 including indicia on one of said wedge and said gear to indicate changes in position of said cylinder relative to said gears when effecting changes in bag length.

22. Apparatus for sealing adjacent superimposed plys of a web of heat sealable stock, said apparatus comprising: web feeding means for supplying web to a rotating sealing cylinder; means for at least partially severing said web of stock and for sealing plys along areas adjacent to and on opposite sides of said partial severance; and means for reducing the velocity of said web as it passes through said means for partially severing said web without stopping the movement of said web.

23. Apparatus in accordance with claim 22 wherein said means for reducing the velocity of said web comprises differential drive means connected to said sealing cylinder to effect a differential rotational velocity to said cylinder during each revolution thereof.

24. Apparatus in accordance with claim 23 wherein said means for at least partially severing said web is mounted in the surface of said cylinder and extends axially thereof; and means for effecting reciprocation of said means into and out of engagement with said web when said cylinder is at its slower portion of its differential rotational velocity.

25. Apparatus in accordance with claim 23 including drive means connected to said differential drive means, said differential drive means comprising a pair of meshing gears each having an offset axis of rotation, one of said gears being connected to said cylinder and the other of said gears being connected to said drive means.

26. Apparatus in accordance with claim 25 wherein said drive means includes a drive motor and variable speed drive means intermediate said drive motor and said pair of meshing gears.

27. Apparatus in accordance with claim 24 including a heat sealing bar connected in timed relation with the rotation of said cylinder and along the opposite side of said web; and means to effect engagement of the severing and sealing means with said sealing bar through said plys of heat sealable material during at least a portion of each revolution of said cylinder.

28. Apparatus in accordance with claim 27 wherein said sealing means is integral with said severing means and underlies said web.

29. Apparatus in accordance with claim 25 including position adjustment means to effect an adjustment of the rotational position of said cylinder relative to said gears.

30. Apparatus in accordance with claim 29 wherein said cylinder includes a shaft mounted for rotation in a frame, and said position adjustment means includes wedge means connected to one of said shaft and one of said gears, and means to releasably couple said wedge to said shaft.

31. Apparatus in accordance with claim 30 including indicia on one of said wedge and said gear to indicate changes in position of said cylinder relative to said gears when effecting changes in bag length.

32. Apparatus for forming bags from a web of thermoplastic stock, said apparatus comprising means for feeding the web continuously through said apparatus, means for severing the web transversely of its length and for sealing areas of the plys along both of the severed edges thereof, and means for reducing the velocity of said web without stopping movement thereof through said severing and sealing means while maintaining the velocity of said feed.

33. Apparatus in accordance with claim 32 including a cylinder mounted for rotation in a frame; differential drive means connected to said cylinder for effectng variations in the rotational velocity of said cylinder during each revolution thereof, said severing and sealing means connected to said cylinder for rotation therewith and for engagement and disengagement with the lower surface of said web during each revolution thereof; and a sealing bar connected for timed rotation with said sealing cylinder, overlying said web transversely 12 thereof; said severing and sealing means being in registry with said sealing bar through said web during each revolution of said cylinder.

34. Apparatus in accordance with claim 33 including means to adjust the speed of said differential drive means to effect changes in bag length without changing the velocity of the feed of said web.

35. Apparatus in accordance with claim 34 wherein said differential drive means comprises a pair of meshing elliptical gears, and means for adjustably coupling one of said gears to said cylinder to permit rotational adjustment of said cylinder relative to said gears when effecting changes in bag length. 

1. Apparatus for sealing and severing adjacent superimposed plys of a web of heat sealable material, said apparatus comprising: web feeding means for supplying said web at a predetermined rate to a severing means; and sealing means associated with said severing means for sealing plys along both of the severed edges thereof; means for reducing the velocity of said web as it passes through said severing means without stopping the movement of said web.
 2. Apparatus in accordance with claim 1 including a sealing cylinder, drive means to effect rotation of said cylinder, and means to effect differing rates of rotational speed to said cylinder during one revolution thereof.
 3. Apparatus in accordance with claim 2 wherein said severing and sealing means are in said cylinder, a heat sealing bar connected in timed relation with the rotation of said cylinder and means to effect engagement of the severing and sealing means in said cylinder and said sealing bar through said plys of heat sealable material during at least a portion of one revolution of said cylinder.
 4. Apparatus in accordance with claim 2 wherein said severing and sealing means is positioned in said cylinder along one side of said web, and means for reciprocating said severing means for engagement and disengagement with said web.
 5. Apparatus in accordance with claim 4 including a heat sealing bar connected in timed relation with the rotation of said cylinder and along the opposite side of said web; and means to effect engagement of the severing and sealing means with said sealing bar through said plys of heat sealable material during at least a portion of each revolution of said cylinder.
 6. Apparatus in accordance with claim 5 wherein said sealing means underlies said web.
 7. Apparatus in accordance with claim 4 wherein said web is engaged by said severing means during the slower portion of the rotational speed of said cylinder.
 8. Apparatus in accordance with claim 2 wherein said drive means includes a drive motor, and said means to effect differing rates of rotational speed comprises a pair of meshing elliptical gears.
 9. Apparatus in accordance with claim 8 including variable speed drive means intermediate said drive motor and said elliptical gears.
 10. Apparatus in accordance with claim 2 wherein said means for sealing said plys is integral with said severing means.
 11. Apparatus in accordance with claim 10 wherein said severing means comprises a knife extending laterally of said cylinder, and means to heat said knife.
 12. Apparatus in accordance with claim 11 including cooling means in said cylinder.
 13. Apparatus in accordance with claim 2 including a discharge conveyor for discharging severed and sealed bags from said cylinder.
 14. Apparatus in accordance with claim 2 including stripping means cooperating with said cylinder to strip bags from said cylinder.
 15. Apparatus in accordance with claim 14 including means defining lands and grooves in the surface of said cylinder, said stripping means comprising a plurality of wheels mounted for rotation in said grooves, and for removing bags from the lands.
 16. Apparatus in accordance with claim 15 wherein said wheels are mounted on a shaft, and bag discharge conveying means rotating said shaft in the same direction as said cylinder.
 17. Apparatus in accordance with claim 15 wherein said severing and sealing means comprises a heated knife, means in said cylinder for receiving said knife, and means to reciprocate said knife between a recessed position below the surface of said cylinder and an elevated position for engagement and diSengagement with said web.
 18. Apparatus in accordance with claim 17 including cam means for disengaging said wheels from said grooves at least when said knife underlies said wheels.
 19. Apparatus in accordance with claim 2 wherein said means to effect differing rates of rotational speed comprises a pair of meshing gears having offset axes of rotation, and means to effect an adjustment of the rotational position of said gears relative to said cylinder.
 20. Apparatus in accordance with claim 19 wherein said cylinder includes a shaft mounted for rotation in a frame, and said means to effect adjustment of the rotational position of said gears comprises a wedge connected to one of said shaft and one of said gears, and means to releasably couple said wedge to said shaft.
 21. Apparatus in accordance with claim 20 including indicia on one of said wedge and said gear to indicate changes in position of said cylinder relative to said gears when effecting changes in bag length.
 22. Apparatus for sealing adjacent superimposed plys of a web of heat sealable stock, said apparatus comprising: web feeding means for supplying web to a rotating sealing cylinder; means for at least partially severing said web of stock and for sealing plys along areas adjacent to and on opposite sides of said partial severance; and means for reducing the velocity of said web as it passes through said means for partially severing said web without stopping the movement of said web.
 23. Apparatus in accordance with claim 22 wherein said means for reducing the velocity of said web comprises differential drive means connected to said sealing cylinder to effect a differential rotational velocity to said cylinder during each revolution thereof.
 24. Apparatus in accordance with claim 23 wherein said means for at least partially severing said web is mounted in the surface of said cylinder and extends axially thereof; and means for effecting reciprocation of said means into and out of engagement with said web when said cylinder is at its slower portion of its differential rotational velocity.
 25. Apparatus in accordance with claim 23 including drive means connected to said differential drive means, said differential drive means comprising a pair of meshing gears each having an offset axis of rotation, one of said gears being connected to said cylinder and the other of said gears being connected to said drive means.
 26. Apparatus in accordance with claim 25 wherein said drive means includes a drive motor and variable speed drive means intermediate said drive motor and said pair of meshing gears.
 27. Apparatus in accordance with claim 24 including a heat sealing bar connected in timed relation with the rotation of said cylinder and along the opposite side of said web; and means to effect engagement of the severing and sealing means with said sealing bar through said plys of heat sealable material during at least a portion of each revolution of said cylinder.
 28. Apparatus in accordance with claim 27 wherein said sealing means is integral with said severing means and underlies said web.
 29. Apparatus in accordance with claim 25 including position adjustment means to effect an adjustment of the rotational position of said cylinder relative to said gears.
 30. Apparatus in accordance with claim 29 wherein said cylinder includes a shaft mounted for rotation in a frame, and said position adjustment means includes wedge means connected to one of said shaft and one of said gears, and means to releasably couple said wedge to said shaft.
 31. Apparatus in accordance with claim 30 including indicia on one of said wedge and said gear to indicate changes in position of said cylinder relative to said gears when effecting changes in bag length.
 32. Apparatus for forming bags from a web of thermoplastic stock, said apparatus comprising means for feeding the web continuously through said apparatus, means for severing the web transversely of its length and for sealing areas of the plys along both Of the severed edges thereof, and means for reducing the velocity of said web without stopping movement thereof through said severing and sealing means while maintaining the velocity of said feed.
 33. Apparatus in accordance with claim 32 including a cylinder mounted for rotation in a frame; differential drive means connected to said cylinder for effectng variations in the rotational velocity of said cylinder during each revolution thereof, said severing and sealing means connected to said cylinder for rotation therewith and for engagement and disengagement with the lower surface of said web during each revolution thereof; and a sealing bar connected for timed rotation with said sealing cylinder, overlying said web transversely thereof; said severing and sealing means being in registry with said sealing bar through said web during each revolution of said cylinder.
 34. Apparatus in accordance with claim 33 including means to adjust the speed of said differential drive means to effect changes in bag length without changing the velocity of the feed of said web.
 35. Apparatus in accordance with claim 34 wherein said differential drive means comprises a pair of meshing elliptical gears, and means for adjustably coupling one of said gears to said cylinder to permit rotational adjustment of said cylinder relative to said gears when effecting changes in bag length. 